Recently, the importance of data backup for data erasure problem has increased with increase in volume of data to be stored in an information processing device such as a server. As a device for backing up large-volume data, there has been widely used a magnetic tape device exemplified by LTO (Liner Tape-Open). In the case of LTO, as much as 1.6 Tbytes data can be recorded on a half-inch width magnetic tape at a transmission rate of 120 Mbytes/sec or more.
The magnetic tape device is provided with a magnetic head for recording data on a magnetic tape or reading data recorded on the magnetic tape. The magnetic head is of a linear recording type, wherein since data is to be recorded and reproduced at each of a plurality of tracks defined along a longitudinal direction of the magnetic tape, a plurality of recording and reproducing elements corresponding to the individual tracks are arranged along a magnetic tape width direction. Typically, the magnetic head has recording and reproducing elements for 16 channels. In the production of the magnetic head, accordingly, even when only one element for one channel is malfunctioning, the entire device becomes a defective product, extremely lowering the yield.
In order to control the quality of reproducing elements formed on a wafer in the production of the magnetic head, a plurality of evaluation elements may be formed in a plurality of areas of the wafer. For example, the evaluation elements are formed by variously changing the MR height of the reproducing element from that of the product element and contribute to estimate of the quality of reproducing elements by measuring resistance characteristics for each MR height. As used herein, the MR height refers to a height of a reproducing element with reference to a tape bearing surface (TBS) to be brought into sliding contact with a magnetic tape and is an important factor in determining electrical characteristics of the reproducing element. A technology of forming such evaluation elements on a wafer is disclosed in Japanese Unexamined Patent Application Publication 7-134811, for example.
However, the evaluation elements formed on the wafer also require an area for disposing lead-out conductive films and electrode films in connection therewith, which extremely reduces an area for formation of the reproducing elements. Accordingly, although the quality can be effectively controlled by the evaluation elements, there arises a problem that the number of recording and reproducing elements that can be obtained from a single wafer will decrease. Considering the fact that the yield of a magnetic head is extremely low, as described above, this is a very serious problem in view of the productivity.
The above problem is inevitable as long as a plurality of elements and evaluation elements are formed on a common layer of a wafer and therefore is not peculiar to a wafer that is to be used for manufacturing a magnetic head but also occurs in a wafer that is to be used for manufacturing other electronic components such as an integrated circuit.